In one aspect, this invention relates to the separation of ethers and aliphatic hydrocarbons from alcohols by extractive distillation. In another aspect, this invention relates to the recovery of ethers from a mixture containing ether(s), alcohol(s) and aliphatic hydrocarbon(s).
Extractive distillation is a well known technique for separating mixtures of components which exhibit relative volatilities close to unity (i.e., having nearly equal volatility and having nearly the same boiling point) and/or which form azeotropes (such as mixtures of ethyl-t-butylether and ethanol). It is difficult to separate the components of such mixtures by conventional fractional distillation. In extractive distillation, a solvent is introduced into a distillation column above the entry point of the feed mixture which is to be separated. The solvent affects the relative volatility of the feed components and/or attractive forces between components of azeotropes sufficiently to facilitate the separation of the various feed components by distillation, as has been described in the article entitled "Extractive Distillation Saves Energy" by Ian Sucksmith, Chemical Engineering, Jun. 28, 1982, pages 91-95. Other literature sources on extractive distillation techniques include "Handbook of Separation Techniques for Chemical Engineers" by Philip A. Schweitzer, McGraw-Hill Book Company, 1979, pages 1-135 to 1-143; and Perry's Chemical Engineers Handbook, 6th Edition, McGraw-Hill Book Company 1984, pages 13-53 to 13- 57.